In order to land on a variety of surfaces, many helicopters are equipped with two parallel skids, extending longitudinally on opposite sides of the helicopter. Moving such helicopters into their hangar or maintenance facility has always been a problem for operators and has resulted in a variety of systems to solve the problem.
The most basic system is to fit the skids with factory supplied wheels and two or more people then balance, maneuver, and roll the helicopter as needed. The disadvantage of this system is that the fitting of the wheels to the skids is time consuming and requires two or more people.
A second system of moving helicopters is to land the helicopters on a rolling platform and tow the helicopter where needed. The disadvantage of this system is the need to tow the device with a power unit. Furthermore, the rolling platform takes up valuable hangar space, presents a more dangerous landing situation, and requires the helicopter to be started up and landed on the platform in order to move the helicopter.
A third system involves a dolly of various configurations that rolls under the helicopter from the front and lifts the helicopter by an apparatus that either slides under the skids, attaches to adaptors on the skids, or engages lifting points on the underside of the helicopter. The dolly lifts the helicopter and is then towed by a separate power unit or is self-propelled, in which case the operator steers from a position in front of the helicopter with a steering arm or handle. Dollies of this type include hardware to stabilize the helicopter and keep the helicopter from teetering on the lifting apparatus. Dollies of this type cannot be used on helicopters with lights or other equipment that are mounted on the underside of the aircrafts since the dollies roll under the aircraft from the front and there is insufficient clearance. Further disadvantages relate to the difficulty of maneuvering the dolly and helicopter when backing up. The operator at the front is a considerable distance from the end of the tailboom. This fact, coupled with the inherent difficulty of backing any four-wheeled vehicle with a conventional steering configuration and the impossibility of pivoting action, makes maneuvering in tight situations, as are often encountered in crowded hangars, very difficult. A further disadvantage of this type of dolly is the problem of insuring that the lifting apparatus is properly aligned with the lifting points on the aircraft. The control for the lifting apparatus, usually mounted on the handle, does not permit the operator a good view of all the lifting points as the apparatus is raised.
A fourth system of handling helicopters on the ground involves devices that directly support the skids, such as U.S. Pat. No. 4,516,744 issued to Burnside, utilizing a caster assembly in the front and a wheel and axle assembly in the rear of the aircraft. Disadvantages of this sytem include the time-consuming nature of positioning the wheel and axle assemblies, and the requirement of a separate power unit for motive power.